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Cisco Bug: CSCvu19105 - LLDP packets with destination MAC of 01:80:c2:00:00:03 cause N3K to learn the source mac address

Last Modified

Aug 05, 2020

Products (58)

  • Cisco Nexus 3000 Series Switches
  • Cisco Nexus 9516 Switch
  • Cisco Nexus 3548 Switch
  • Cisco Nexus 3636C-R Switch
  • Cisco Nexus 3548-X Switch
  • Cisco Nexus 31108TC-V Switch
  • Cisco Nexus 3132Q-V Switch
  • Cisco Nexus 9396PX Switch
  • Cisco Nexus 93108TC-FX Switch
  • Cisco Nexus 9396TX Switch
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Known Affected Releases

7.0(3)I7(8) 9.2(3)

Description (partial)

Symptom:
LLDP packets with destination mac of 01:80:c2:00:00:03 cause N3K learning the mac address

One use-case where this can be an issue is when a server with an active/standby pair of NICs connects to a vPC pair and both active and standby NICs send LLDP packets using the same virtual Source MAC. Due to this defect, the switch learns the source MAC when it receives LLDP packets from the standby NIC, causing blackholing due to traffic  being sent to the standby NIC instead.

F340.09.04-N3K-5# ethanalyzer local interface inband display-filter lldp limit-captured-frames 0

Capturing on inband
2020-05-09 08:18:08.142174 3c:51:0e:44:db:80 -> 01:80:c2:00:00:03 LLDP Chassis Id = 3c:51:0e:44:db:80 Port Id = Ethernet1/32 TTL = 120 System Name = N9336-2
2020-05-09 08:18:13.142156 3c:51:0e:44:db:80 -> 01:80:c2:00:00:03 LLDP Chassis Id = 3c:51:0e:44:db:80 Port Id = Ethernet1/32 TTL = 120 System Name = N9336-2
2020-05-09 08:18:14.322279 00:62:ec:40:4f:c8 -> 01:80:c2:00:00:0e LLDP Chassis Id = 00:62:ec:40:4f:c8 Port Id = Ethernet1/1 TTL = 120 System Name = F340.09.04-N3K-5


F340.09.04-N3K-5# show lldp neighbors
ERROR: No neighbour information

F340.09.04-N3K-5# show mac address-table
Legend:
        * - primary entry, G - Gateway MAC, (R) - Routed MAC, O - Overlay MAC
        age - seconds since last seen,+ - primary entry using vPC Peer-Link,
        (T) - True, (F) - False, C - ControlPlane MAC, ~ - vsan
   VLAN     MAC Address      Type      age     Secure NTFY Ports
---------+-----------------+--------+---------+------+----+------------------
*  921     3c51.0e44.db80   dynamic  0         F      F    Eth1/1                 <<<<<<<<<<<<<<

Conditions:
peer device send lldp packets with the Dmac address of 01:80:c2:00:00:03
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Bug Details Include

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